The present invention relates to an electrical bar cutting tool, an electrical bar bending tool, and an electrical bar cutting and bending tool. The electrical bar cutting tool or bar cutter is used for cutting an elongated member such as a steel rod and a metal pipe, and the electrical bar bending tool or bar bender is used for bending the elongated member. Further, the electrical bar cutting and bending tool or a bar cutter/bender is used for selectively cutting or bending the elongated member.
A portable electric cutting and bending tool is capable of cutting to a desired length or bending an elongated rod such as steel rods or pipes used in the construction of houses or buildings, in engineering work, and the like. The following descriptions use the example of reinforcing rods as the object to be cut or bent.
A large amount of reinforcing rods are used to reinforce concrete in house and building foundations, block walls, and structures used in engineering work. Reinforcing rods have fixed standard diameters of 10, 13, 16, 19, and 22 mm and are generally sold at a fixed length of 5 meters.
FIG. 34 shows the variety of patterns in which reinforcing rods 70 are cut and bent for use in the foundation of a house. These rods are cut to specified lengths, bent to specified angles, and assembled together with binding wires 74 according to construction blueprints. For example, a reinforcing rod 72 with a diameter of 10 mm is cut to a length of about 1 m and bent into an L-shape at 90.degree., and a reinforcing rod 73 with a diameter of 13 mm is cut to a length of about 1.2 m, after which the top end is bent into a U-shape at 180.degree.. A tool is needed for cutting these reinforcing rods to desired lengths and bending them to desired angles between 45 and 180.degree..
Conventionally, manufacturers of the rods cut and bend hundreds to thousands of the reinforcing rods at one time using a large machine built specially for such work. The manufacturers then supply these rods to the builders. However, it can be quite expensive to hire the services of these manufacturers when using a comparatively low 200-400 rods per day, for example when making additions or modifications at the construction site of an ordinary house, outer structure, or building. If there is a lot of processing work at the construction site, it may be necessary to cut and bend reinforcing rods on the site in order to conform to the actual situation. In this case, cutting and bending must be accomplished with a cutting and bending tool as described in Japanese Patent Application Kokai (OPI) No. SHO-56-144826.
In the bar cutter/bender disclosed in the Japanese reference, an output shaft extends in a housing and is driven by a drive motor through a speed reduction gear mechanism. An eccentric cam is provided integrally with the output shaft at an intermediate portion of the output shaft and inside the housing. A slide piece is provided movable in a direction perpendicular to the output shaft. One end of the slide piece is provided with a cam roller in contact with the cam surface of the eccentric cam, and another end of the slide piece is provided with a movable blade. Upon rotation of the output shaft, the slide piece is moved by the eccentric cam, so that the movable blade is moved toward a stationary blade to cut the elongated member.
Further, an end portion of the output shaft protrudes from the housing, and a crank-shaped pivot plate provided with a bending roller is connected to the output shaft. Further, a center roller is coaxially provided with the protruded part of the output shaft. Therefore, the bending roller is moved along an arcuate path about the center roller upon rotation of the output shaft. The elongated member such as a steel rod is bent at a position around the center roller by the urging force of the bending roller.
However, the cutting and bending tool disclosed in the JP reference is disadvantageous in portability, size, weight and production cost. More specifically, a large cutting force is required to cut reinforcing rods. For example, 56,000 N of force is required to cut a reinforcing rod having a diameter of 13 mm. However, the slide piece does not provide a power boosting function. Therefore, the pushing force of the eccentric cam on the cam roller of the slide piece must be 56,000 N, requiring the output shaft and the eccentric cam supported thereby to be very large and heavy in order to support such force. As a result, the gear train and electric motor will also have to be large to drive the heavy output shaft and eccentric cam.
Further, the eccentric cam is exclusively used for cutting, and the pivot plate is exclusively used for bending, and these are positioned spaced away from each other. Therefore, these components must be respectively manufactured and assembled. These many parts will not only make the overall tool heavy, but will require the output shaft to be longer in accordance with the provision of the eccentric cam at the intermediate portion of the output shaft. As a result, the tool will be too large to be appropriate as a portable tool, and production cost is greatly increased.
A manually operated bar bender is also known. Even though manual operation requires operator's force, delicate and adjustive bending can be performed while observing the bending state of the bar. In contrast, a conventional electrically operated bar bender cannot perform an adjusted bending operation due to rapid bending.
A hydraulically operated bar cutter is also known. Generally, the hydraulic bar cutter requires a great number of oils to be supplied into a cylinder, and long moving stroke results, to prolong the operation period.
A Japanese Patent Application Kokai (OPI) No. Hei 4-262824 discloses a steel bar bender as shown in FIG. 35. A steel bar bending operation is performed on a top plate 205, and a bending roller 214 and a center pin 204 are provided at a position above the top plate 205. An electric motor is disposed immediately below a top plate 205. Rotation of the electric motor is transmitted to an output shaft through a gear train. Because the electric motor has a relatively large mass, the top plate 205 is positioned at a relatively high position, where the bending operation is performed.
With this arrangement, the steel bar 226 is pressed by the bending roller 214 and is bent around the center pin 204. If a relatively long steel bar 226 is to be bent, the steel bar 226 must be held by hand such that the steel bar 226 can be contacted with the bending roller 214 and the center pin 204. Further, the height of the steel bar bender is primarily dependent on the size of the electric motor. Therefore, it may be difficult to provide a compact steel bar bender.
FIGS. 36 and 37 show still another conventional steel bar bender. On a top plate 205, a center pin 227 serving as a fulcrum for bending the steel bar and a separate counteraction receiving member 228 are provided. The center pin 227 is fixedly secured to the top plate 205 by a key 229 and a bolt (not shown) in order to stably maintain its position so as not to be moved by the bending steel bar pushed by the movable bending roller 214. With this arrangement, the center pin 227 and the counteraction receiving member 228 must be independently produced and then assembled to the top plate 205, thereby rendering the entire structure intricate. Further, the top plate 205 must be formed of thick steel plate since the top plate 205 must provide sufficient strength capable of sustaining a bending force applied to the center pin 227. As a result, the steel bar bender becomes heavy.
In another aspect, the bar cutter or bar bender is used at an outdoor building site, and a great amount of scales are peeled off from the steel bar 226 during bending operation. Therefore, a dust proof arrangement is required so as to prevent the scales from entering into mechanically engaging portions or an electric motor, to prolong the service life of the bar cutter/bender. However, a dust proof structure has not yet been proposed in this field.
In still another aspect, FIG. 38 shows a conventional bar cutter/bender of a portable and ground set type. The bar cutter/bender provides a change-over switch for changing the bending operation and cutting operation from each other. A cutter portion 231 is exposed at the side surface of a housing. Therefore, if a bending operation is to be performed in spite of the cutting mode, the cutter portion 231 is activated, so that the cutter portion 231 inadvertently bites foreign objects, since the cutter portion is also driven during the bending operation mode.
Further, FIG. 39 shows another conventional steel bar cutter/bender, in which a protective cover 232 is provided so as to cover a cutter portion 231 in case of the bending mode or transportation. However, if an operator forgets the closure of the protective cover 232, the cutter portion 231 may bite the foreign objects during bending operation mode.
In still another aspect, in the conventional steel bar cutter/benders shown in FIGS. 38 and 39, if an elongated steel bar such as the bar having a length of 5 m is to be cut, shaking may occur in the entire device when the heavy steel bar is set on the device or displaced for adjusting the cutting position. Therefore, a stabilized cutting operation may not be performed. A Japanese Patent publication (Kokoku) No. Hei 2-8810 discloses a bar cutter/bender similar to the type shown in FIG. 39.
Further, a Japanese Utility Model Application Kokai (OPI) No. Hei 5-12033 and a commonly assigned copending U.S. patent application Ser. No. 08/429,551 (corresponding to a German Patent Application No. 195 15 955.1) disclose a driving mechanism using a cam for driving a movable blade in a screw bar cutter.
Further, a Japanese Patent Publication (Kokoku) No. Hei 4-38527 discloses a bar cutter/bender. In the bar cutter/bender, a main body is provided with a center roller around which the bar is bent, and a stationary blade. A pivot arm is pivotally supported to the main body. The pivot arm has an intermediate portion provided with a movable blade and a free end portion provided with a bending roller. The pivot arm is connected to a piston, so that the pivot arm is pivotally movable about a pivot shaft mounted on the main body.